1. Field of Invention
The present invention relates to the field of biotechnology. In particular, it relates to the use of human NLK gene and associated drugs thereof.
2. Description of Related Arts
Nemo-like kinase (Nemo-like kinase, NLK) located in the cell nucleus, is a kind of conserved serine-threonine kinase in the proline-mediated protein kinase superfamily, and is initially considered being relevant to the polarization of eye cells of drosophila and the various developmented process of vertebrate (Choi K W et al., Cell (1994) 78: 125-36. Verheyen E M et al., Mech Dev. (2001) 101: 119-32). The recent studies suggest that NLK can adjust, phosphorylate transcription factors, and involve in apoptosis of cells through various signaling pathways (Brott B K et al., Proc Natl Acad Sci USA. (1998) 95: 963-8. Mirkovic I et al., Mech Dev. (2002) 119: 9-20).
Wnt signaling transduction pathways include: extracellular factor (Wnt), transmembrane receptors (Frizzled, Fz), cytoplasmic proteins (Dsh, β-catenin/APC/Axin complexes, etc.) and nuclear transcription factor (TCF/LEF), which are closely related to the occurrence and development of various tumors (Bienz M et al., Cell (2000) 103: 311-20). NLK is a negative regulator of Wnt/β-catenin signaling pathway, and may phosphorylate TCF/LEF to inhibit the transcriptional activity of β-catenin/TCF complex. C-Myb protein, as the c-myb proto-oncogene expressed product, is deemed as a transcription factor to regulate various downstream gene transcriptions, thereby affecting the proliferation and apoptosis of hematopoietic stem cells. Through transforming growth factor β-activated kinase TAK1, Wnt-1 induces NLK to directly bind with and phosphorylate c-Myb protein at multiple sites, which undergoes subsequently the degradation of ubiquitination and proteasome-dependent, further may cause cell cycle arrest in G1 phase. However, the regulation of a-Myb, which is another member of the Myb family, mainly is the phosphorylation and the inhibition of its binding with the DNA-binding domain to function (Kanei-Ishii C et al., Genes Dev. (2004) 18: 816-29). Besides, Research has found that, the phosphorylation of TAK1-NLK pathway has transcription factor FOX01 affecting cell apoptosis, stress, DNA damage/repair and tumorigenesis, and prompts the shift of FOXO1 from the nucleus to the cytoplasm, thereby inhibiting the transcriptional function of FOX01 (Kim S et al., J Biol Chem. (2010) 285: 8122-9). Further research has found that, through the phosphorylation of C-terminal region of the transcriptional coactivator factor CBP/P300, NLK further involves in the process of cell apoptosis by way of affecting the transcriptional activity of transcription factors, e.g.  Smad and the like (Yasuda J et al., Cancer Sci. (2004) 95: 52-7. Shi Y et al., Mol Cell Biochem. (2010) 333: 293-8).
With respect to the research of NLK in tumor, there have been reports of colorectal cancer, prostate cancer and hepatocellular carcinoma. NLK is considered as a tumor suppressor gene of Wnt/β-catenin signaling pathway in colorectal cancer. Wild-type NLK in colorectal cancer is induced to express, and inhibits cell growth through the phosphorylation of TCF/LEF, and promotes cell apoptosis via p53-independent, but does not affect cell cycle (Yasuda J et al., Biochem Biophys Res Commun. (2003) 308: 227-33). In prostate cancer, NLK negatively regulates the signal transduction pathway of androgen receptor. The overexpression of NLK can significantly induce the apoptosis of prostate cancer cell with positive expression of androgen receptor. Further research has found that, by forming complex with androgen receptor, NLK enables the inhibition of androgen receptor from the transcriptional activity of target genes and the depression of androgen receptor mRNA at transcriptional level (Emami K H et al., Prostate. (2009) 69: 1481-92). In human hepatic carcinoma cell lines, the knockout of NLK expression can inhibit cell growth. Meanwhile, it is found that, as the increase of G1-S phase cells, the expression of cell cycle-related proteins cyclin D1, CDK2 decreases significantly, which indicates that NLK may give play to the effect of promoting mitosis by acting on cyclin D1 CDK2 in the formation of liver cancer. (Jung K H et al., J Cell Biochem. (2010) 110: 687-96). Above all, NLK plays different biological functions during the occurrence and development of different tumors.
RNA interference (RNA interference, RNAi) refers to a short double-stranded RNA (dsRNA) composed of nucleotides performs post-transcriptional gene silencing. It can efficiently and specifically block the expression of certain genes in vivo, cause them to degrade, thereby resulting in the silencing of specific genes in vivo and making cells exhibit a kind of phenotype deletion, which is a rising laboratory technique commonly used to study gene functions and to search a cure for disease in recent years. Research shows that double-stranded RNA with a length of 21-23 nt can specifically cause RNAi at transcription and post-transcriptional level (Tuschl T et al., Cell (2000) 101: 25-33). In spite of chemotherapy, radiotherapy, and combination therapy, the five-year survival rate for tumor patients is still quite low. New approaches in tumor treatment could be opened up if the genes relating to the onset and progress of tumors could be subjected to RNA interference. In recent years, RNAi has become an effective strategy for tumor gene therapy. The use of RNAi techniques can inhibit the expression of oncogenes, mutated tumor suppressor genes, cell cycle-related genes, and anti-apoptosis genes and thereby inhibiting the course of tumors (Uprichard et al., FEBS Letters (2005) 579: 5996-6007).
In order to further study the regulatory function of NLK in tumorigenesis, the cell models of lung cancer, breast cancer and prostate cancer is selected in the present invention, to study the roles of NLK in the occurrence and development of lung cancer, breast cancer and prostate cancer by means of RNAi.